Treatment of earthy minerals



Pasta Mar. '22, 1927.

UNITED STATES .WILLIAH FELDENHEILIER, OF LONDON, ENGLAND.

TREATMENT DI EARTHY MINERALS.

Re Drawing.

invention relates to the treatment of clays or like earthy minerals for their puria fication and improvement of their color.- In

my copending applica'tion,-Serial No 33,051, filed May 26, 1925 I have described the treatment of such minerals with an acid salt of sulphurous acid in the presence oi a metal such as zinc. I have now discovered that instead of bringing the earthy mineral in con tact with acid salt of sulphurous acid in the actual presencev of metallic zinc 'or other metal, I can prepare a bleaching liquid by digesting the zinc or other metal in a salt of sulphurous acid and can thereafter treat the earthy mineral, such as clay slip, with this liquor and obtain a result similar to that of the process of my copending application above referred to Without the presence of the metal in the treatment bath. The zincor such as sulphurous acid, has certain disadvantages in commercial use. The acid diificult to handle and liable to attack the plant apparatus; and is also readily oxidized to produce the more corrosive sulphuric acid. The action of sulphurous acid upon metal tendsto be localized by reason of the use of a gas and in bulk operationit is diflicult to insure uniform treatment of .the mineral.

In accordance with the present invention, the earthy mineral such as clay which is to be improved in color, is brought into con-' A difiiculty in the bleaching of clay is that the clay after having been" treated with bleaching agents becomes recolored upon drying, and if a metal, such as iron, which yields colored oxidized salts to be employed in the reaction, the'object of the bleachin but if used in every dilute'concentration such metal may as. a catalyst hasten the bleaching.

It is of advantage attimes, in order to.

accelerate the r'eaction,-to add to a trace of 'a mineral acid to the reaction mixture, preferably an acid which yields the less readily oxidized salts of iron, for example, hydrochloric acid. Bleaching willproceed, hqw,-

Applicationfl1ed October so, 1925, serial No. 65,892.

ever, without the presence of the acid.

Sodium sulphite may be used with zinc for example, provided'a small quantity of acid such as hydrochloric acid is present. Since the earthy minerals-and clays differ in character, the treatment must be varied according to the particular earthy mineral being treated.- i?

In'carrying the invention into effect, care should be observed to maintain efficient agitation of the mineral suspension throughout the operation in order to insure as complete.

and uniform an action as possible. upon the mineral,

, I have found that the liquor formed b d1-, gesting zinc in sodium bisulphite or sodium metabisulphite' will bleach cert'ain' clays which are not bleached by zinc and sulphurous acid.-

other metal should be in excess in this step. Asstated in the specification of my application Serial No. 33,051, the use of an acid The liquor which I employ probably contains sodium hydrosulphite, sodium sul hite and sulphite of zinc or other metal emp oyed and the present process is an improvement over that of m copending case, in that no provision need e made for the presence of a metal such as zinc, in the bath where the clay or earthy mineral is treated.

I With the use of my invention the bleaching action is more eflicient and rapid and extends throughoutthe bath instead of being localized.

Acidity rapidly liberating the acids and gases which carryout the bleaching action.

The coloring matter may be decanted ,ofi with the excess water; and this should be if used, is only of advantage indone if the fluid is exposed to air and sunlight as substances in the upper water layer will usually become yellowish or brownish on such exposure. .Changes may-be made in the particular salt of sulphurous acid and in the metal em-. ployed provided the metal reduces S0,. I claim:. 1 a

1. In the process for improving the color of earthy minerals, the step comprising ring-' 7 g ing-an aqueous suspension of the sub-divided process may .be partly or wholly -defeated,-

mineralint'o contact with a salt'of sulphur-' ous .acid containing a salt of a metal which reduces sul hurous acid and does .not form of the sub-divided mineral a salt of sulphur,

ous acid containing a salt of zinc.

3. In the process for improving the color of clay, the step consisting in bringing in contact with the clay in suspension in water a sulphite salt of sodium in the presence of a salt of a metal which reduces sulphurous acid and does not form colored oxidized sodium metabisulphite iii the presence of a salt of zinc. I

5. In the process. for improving the color of clay, the step consisting in bringing in r a sulphite' salt of sodium in the preseince of acid and a salt of a metal which reduces sulphurous acid and does not form colored oxidized salts. p v

6. In the process for improving the color of clay, the step consisting in bringing into contact with the clay in suspension in'water a salt of hydrosulphurous acid and a salt of a metal which reduces sulphurous acid and does not form colored oxidized salts.

In testimony whereof I have hereunto set my hand.

WILLIAM FELDENHEIMER. 

